FOM - 16.0160
Annual report 2015
FOM programme nr. 129
'Fundamental aspects of friction'
Foundation for Fundamental Research on Matter
www.fom.nl
Novel experiment developed at Uva in which pressure sensitive molecules are used to probe the contact area
at the nanoscale, thereby putting the Amonton's law of friction to a test.
May 2016
Content
1. Scientific results 2015 ................................................................................................................................ 3
2. Added value of the programme .............................................................................................................. 5
3. Personnel .................................................................................................................................................... 5
4. Publications ................................................................................................................................................ 5
5. Valorisation and outreach ........................................................................................................................ 5
6. Vacancies .................................................................................................................................................... 5
Fact sheet as of 1 January 2016...................................................................................................................... 6
Historical overview of input and output .................................................................................................... 8
PhD defences ................................................................................................................................................... 8
Patents (new/changes) .................................................................................................................................. 8
Overview of projects and personnel ............................................................................................................ 9
Workgroup FOM-A-03 .................................................................................................................................. 9
Workgroup FOM-D-54 .................................................................................................................................. 9
Workgroup FOM-D-55 .................................................................................................................................. 9
Workgroup FOM-G-17 .................................................................................................................................. 9
Workgroup FOM-L-14 ................................................................................................................................. 10
Workgroup FOM-N-24 ................................................................................................................................ 10
Workgroup FOM-T-17 ................................................................................................................................. 10
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1. Scientific results 2015
The programme 129, 'Fundamental aspects of friction' has had several successes, both in terms of
scientific results and personal development. In fact one of the PhD students , now
Dr. Merel van Wijk , has successfully completed the PhD and another, Fei Liu, has planned the
defense, and Dr. Lucia Nicola has received an ERC starting grant with title 'A seamless multi scale
model for contact, friction and solid lubrication' on a theme stemming from her research in the
programme. The work of the different partners has been presented in several (invited) talks at
international conferences and published in excellent journals as described below.
The individual projects range from friction in nanoscale systems, mostly based on graphitic materials, to the effect of plastic deformations at asperities in the contact area which are important for
metals, to visualization of frictional contacts based on fluorescent molecules, and friction at solid/
liquid interface. The efforts of previous year in development of experimental and theoretical
methods has led to exciting new results, like the optical visualization of the basic laws of friction
shown on the cover at the University of Amsterdam , the demonstration of reliability of scanning
probe for liquids at University of Twente, a new approach to the theoretical description of moiré
patterns in graphitic structures at the Radboud University.
Below some more specific results of the involved groups.
Erik van der Giessen (RUG) The majority of computational studies at the mesoscopic scale have
dealt with unit events, such as the shearing of two contacting asperities, in order to get a fundamental understanding of the influence of size-dependent material behavior. Currently, however,
the team in Groningen is working on simulations of realistic rough surfaces, albeit using a simpler
size-dependent material model. Finally, as promised in the original proposal, they are working on
embedding their discrete dislocation simulations with the statistical description of realistic surfaces
proposed by A. Vakis (from the ENgineering and TEchnology institute Groningen, ENTEG). These
two studies constitute the final part of the PhD thesis of H. Song.
Lucia Nicola (TUD) Plastic shearing of microscale asperities is size-dependent. Unexpectedly, the
contact shear stress, which is closely related to the friction stress is not controlled by the size or the
shape of the asperity. This is because dislocations are not confined to the asperity itself but glide
much deeper in the underlying crystal. It is the contact area which instead determines the size of
the highly stressed region where dislocations can nucleate, and by that controls plastic deformation. If the rate of nucleation is not sufficient to sustain plastic deformation, the friction stress
reaches high values and promotes sliding of the contact.
The microscale simulations show many dislocations piled up at the contacts. To verify whether
this is realistic or if dislocations would rather glide out of the contact or re-nucleate in the crystal if
given the possibility, molecular dynamics simulations are performed (the two papers we are
finalizing). The simulations study individual dislocation impingement on contacts, but also the
impingement of a train of dislocations when a bi-crystal is subjected to normal loading. Only when
very large loads are applied, corresponding to a few GPa stress state in the crystals, the length of a
dislocation pile-up is found to be limited by re-nucleation to few dislocations. The behavior of
dislocations after impingement is found to be strongly dependent on the atomic scale roughness of
the bi-crystal interface. The stress of re-nucleation of dislocations from the interface is found to be
directly related to its roughness, while no correlation is found with interfacial energy.
Frieder Mugele (University of Twente) In previous work, the group showed that the thermal noise
spectroscopy (TNS) is reliable for force measurements in liquid. However, it is time-consuming.
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Therefore, TNS was used as a benchmark to validate a faster (but often criticized) approach-amplitude modulation with piezo excitation (AM-AFM). The results from AM-AFM were compared to those from TNS in the measurements of DLVO forces, hydration forces, and dissipation
and it was found that AM-AFM with piezo excitation is also quantitatively reliable if the fluid
excitation is taken into account.
The hydrodynamic dissipation is enhanced in overlapping electrical double layers and the
enhancement is correlated with surface charge density. The enhancement is qualitatively explained
by the conventional Poisson-Boltzmann theory and hydrodynamics in the continuum regime. A
quantitative understanding is not achieved yet, which may ask for insights into ionic transport at
charged interfaces and hydration dissipation in the non-continuum regime.
D. Bonn, A.M. Brouwer (UvA) The friction coefficient is defined as the ratio between friction force
and normal force, and is usually taken independent of the surface area of the sliding object.
According to Amontons' law, this can be done because the contact area is proportional to the normal force and the friction force, in turn, is proportional to the contact area. However, little is
known about the contact area, because it is hidden between two bulk phases and it can have
roughness down to the molecular length scale. At the university of Amsterdam, we develop a
novel experiment in which pressure sensitive molecules are used to probe the contact area down to
this length scale. This allows us to put Amontons' law to the test; we find that although the friction
force is proportional to the contact area, the latter is not proportional to the normal force. We
reproduce the experimental results with molecular simulations and show that frictional contacts
are elastic and there is no necessity to invoke plastic deformation of the surface asperities.
Merlijn van Spengen (TUD) I n 2015, we have performed measurements with the polycrystalline
silicon MEMS adhesion and friction sensor devices with locally heated heads and counter-surfaces,
which were developed earlier in the project. These measurements were performed with (for
MEMS) unprecedented resolution, due to the new optical displacement measurement method that
we developed in a recent STW Vidi project. The adhesion measurements show high, irregular
adhesion around 70 C, and low and stable adhesion significantly above the boiling point of water.
At very high temperatures we see the effect of direct bonding, which increases the adhesion again.
When studying sliding motion, we observed a lowering of silicon on silicon friction with temperature. But at high temperatures, we observe high-friction irregular stick-slip, presumably due to
the wearing off of the protective native oxide layer on the devices.
The vacuum probe station for local graphene growth, and the corresponding nickel MEMS adhesion and friction sensors with local heaters, have been built as well. They will be used in 2016 to
assess the suitability of locally grown graphene to alleviate the adhesion, friction and wear in
MEMS.
A. Fasolino (RU) The focus of the group is on carbon systems. In a collaboration with
Astrid de Wijn, the solid lubrication of graphenen and graphene flakes has been investigated by
means of realistic molecular dynamics simulations. The individual behavior of the flakes is
important here: low friction has been found as a result of non simultaneous slipping of flakes.
Graphene on top of rotated graphene or on BN presents moiré patterns that involve in-plane and
out-of-plane distortions of relevance for friction. A hierarchical model has been proposed to couple
atomistic classical simulations to electronic structure, showing the effects of distortions due to
weak van de Waals interactions. The group has also collaborated with the group of Novoselov in
Manchester to explain the rotations of micron sized graphene on BN. A paper in Nat. Comm. is in
print.
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2. Added value of the programme
Several formal and informal collaborations between the partners have taken place. The programme
has led to synergy of the findings by the students in the groups of Nicola (TUD) and
Van der Giessen (RUG). This is reflected in a joint publication where their findings could be fused
into a more embracing understanding (see Song et al. (2015) in section 4). On the other hand, the
intended collaboration with the experimental groups in Delft and Amsterdam did not materialize,
because in retrospect the plans for this were not sufficiently clear at the time of writing the proposal. The cohesion within the programme has been also partially affected by the departure of the
original coordinator Prof. Joost Frenken (now at ARCNL) and the announced change of career of
Dr. Merlijn van Spengen (TUD). In the coming period meetings are planned to evaluate the possibility of continuing the research on fundamental properties of friction with new plans and possibly
additional partners
3. Personnel
Two PhD have finished and one is almost ready.
4. Publications
- R.J. Dikken, E. van der Giessen and L. Nicola, Plastic shear response of a single asperity: a discrete
dislocation plasticity analysis, Philosophical Magazine A, 3845–3858, 2015. doi:
10.1080/14786435.2015.1102982.
- H. Song, R. J. Dikken, L. Nicola and E. van der Giessen, Plastic Ploughing of a Sinusoidal Asperity
on a Rough Surface, J. Appl. Mech 82, 071006, 2015. doi: 10.1115/1.4030318
- Fei Liu, Cunlu Zhao, Frieder Mugele, and Dirk van den Ende, Amplitude modulation atomic
force microscopy, is acoustic driving in liquid quantitatively reliable? Nanotechnology 26,
385703 (2015).
- T. Suhina, B. Weber, C.E. Carpentier, K. Lorincz, P. Schall, D. Bonn, and A.M. Brouwer,
Fluorescence Microscopy Visualization of Contacts Between Objects, Angewandte Chemie 127, 3759
(2015).
- van Wijk, M.M.; Fasolino, A., Minimal graphene thickness for wear protection of diamond, AIP
ADVANCES 5, 017117 (2015).
- M.M. van Wijk, A. Schuring, M.I. Katsnelson, A. Fasolino, Relaxation of moiré patterns for slightly
misaligned identical lattices: graphene on graphite, 2D Materials 2, (2015) 034010 (arXiv:1503.02540).
- G.J. Slotman, M.M. van Wijk, Pei-Liang Zhao, A. Fasolino, M.I. Katsnelson and Shengjun Yuan,
Effect of structural relaxation on the electronic structure of graphene on hexagonal, boron nitride Phys.
Rev. Lett. 115, 186801 (2015).
5. Valorisation and outreach
None.
6. Vacancies
None.
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Fact sheet as of 1 January 2016
FOM - 10.1725/5
datum: 01-01-2016
APPROVED FOM PROGRAMME
Number
129.
Title (code)
Fundamental aspects of friction (FAF)
Executive organisational unit
BUW
Programme management
Prof.dr. A. Fasolino
Duration
2011-2016
Cost estimate
M€ 2.7
Concise programme description
a. Objectives
This programme is focused on bridging the threefold gap between our understanding of frictional
energy dissipation in an ideal, dry, single, elastic nanoscale contact and the practical situation for
sliding bodies of a large ensemble of micrometer-scale, elasto-plastic contacts under dry or
lubricated conditions.
b. Background, relevance and implementation
Friction originates from interactions between stationary or moving bodies on the sub-nanometer
length scale of individual atoms and molecules. Interestingly, its consequences manifest themselves
on much larger scales, thus easily bridging orders of magnitude in scale, up to the micrometer regime
of a single, practical asperity and the macroscopic regime of large ensembles of such asperities on
rough surfaces. Although an impressive body is available of phenomenological knowledge about
friction, surface treatments, the application of special coatings and a wide variety of lubricants, most
of this know-how rests on a purely empirical basis and lacks a thorough understanding of the
microscopic dissipation phenomena that are responsible for the energy loss during sliding. Yet, it will
be through precisely such advanced knowledge that completely new geometries and materials will
be invented that will be at the core of the next generation of genuine breakthroughs in lubrication
and other forms of friction reduction. In view of the large scale of continual loss of energy and
resources in modern society that results from unwanted forms of friction and wear, the economic and
societal impact of breakthroughs in this area of science and technology cannot be overestimated.
We target three major differences between 'idealized', nanoscale contacts and practical situations,
namely (i) the difference between single and multiple contacts, (ii) the difference between purely
elastic and elasto-plastic systems and (iii) the difference between unlubricated and lubricated
contacts. In each case we will identify and investigate the generic physics involved in these
differences, employing a dedicated mix of experimental, theoretical and computational expertise. Our
objective is to reach genuine, fundamental understanding of the phenomenology of friction in (near)practical situations, rooted in a solid description, with predictive power, of the underlying physics on
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all relevant length scales, ranging from the atomic scale to the collective response on the micrometer
level. In the context of this programme we will explore various new strategies to control and lower
friction. A key role in these is reserved for novel materials, graphene and boron nitride, and special
nanopatterns.
When successful, this programme will not only provide improved understanding of the foundations
of macroscopic friction, but it will also lead to novel tools for nano- and microtechnology where the
importance of friction is magnified because of the high surface-to-volume ratio. Our ultimate goal is
to make friction a design parameter, with a specified value, or absent, as desired.
Funding
salarispeil cao per 01-01-2016
bedragen in k€
≥ 2015
2016
2017
2018
2019
2020
≥ 2021
Totaal
FOM-basisexploitatie
2.329
118
-
-
-
-
-
2.447
300
-
-
-
-
-
-
300
Doelsubsidies NWO
-
-
-
-
-
-
-
-
Doelsubsidies derden
-
-
-
-
-
-
-
-
2.629
118
-
-
-
-
-
2.747
FOM-basisinvesteringen
Totaal
Source documents and progress control
a) Original programme proposal: FOM-10.1240
b) Ex ante evaluation:
FOM-10.1414
c) Decision Executive Board:
FOM-10.1724
Remarks
The final evaluation of this programme will consist of a self-evaluation initiated by the programme
leader and is foreseen for 2017.
vH
Subgebieden: 70% FeF, 15% NANO, 15% COMOP
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par. HOZB
Historical overview of input and output
Input
personnel (in fte)
WP/T
PhD
0.8
finances* (in k€ )
2011
WP/V
-
NWP
-
2012
-
-
4.1
-
199
2013
-
-
7.4
-
346
2014
-
-
8.0
-
562
2015
-
-
7.4
-
462
PhD theses
refereed publications
2011
-
2012
133
patents
1
other publications &
presentations
4
1
3
10
-
2013
-
6
21
-
2014
-
5
20
-
2015**
1
10
24
-
Output
14
* After closing the financial year.
** The output of Dr. I.M.N. Groot is not (yet) included.
PhD defences
2011
None.
2013
None.
2015
Merel Marieke van Wijk, 21 December 2015,
FOM-N-24.
2012
G. Dong, 7 November 2012, FOM-L-14.
2014
None.
Patents (new/changes)
2013
None.
2015
None.
2014
None.
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Overview of projects and personnel
Workgroup FOM-A-03
Leader
Prof.dr. D. Bonn
Organisation
University of Amsterdam
Project (title + number)
Quantitative probing of friction in multi-asperity contacts with
fluorescent probes 10FAF06
FOM employees on this project
Name
Position
B.A. Weber
PhD
Start date
15 October 2012
End date
14 October 2016
T. Suhina
1 September 2012
31 August 2016
PhD
Workgroup FOM-D-54
Leader
Dr.ir. L. Nicola
Organisation
Delft University of Technology
Project (title + number)
Single asperity contact and friction 10FAF03
FOM employees on this project
Name
Position
R.J. Dikken
PhD
Start date
1 December 2011
End date
31 March 2016
Workgroup FOM-D-55
Leader
Dr.ir. W.M. van Spengen
Organisation
Delft University of Technology
Project (title + number)
Nanoscale multi-asperity contact adhesion/friction/wear
measurements with MEMS devices 10FAF08
FOM employees on this project
Name
Position
A. Gkouzou
PhD
Start date
19 August 2013
End date
18 August 2017
Workgroup FOM-G-17
Leader
Prof.dr.ir. E. van der Giessen
Organisation
Groningen University
Project (title + number) Mesoscopic modeling of multi-asperity contact and friction 10FAF04
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FOM employees on this project
Name
Position
H. Song
PhD
Start date
1 September 2012
End date
31 August 2016
Workgroup FOM-L-14
Leader
Prof.dr. J.W.M. Frenken
Organisation
Leiden University
Superlubricity, themolubricity and energy dissipation 10FAF01
Project (title + number)
FOM employees on this project
Name
Position
P. Antonov
PhD
Start date
1 October 2012
End date
30 September 2016
Workgroup FOM-N-24
Leader
Prof.dr. A. Fasolino
Organisation
Radboud University Nijmegen
Project (title + number)
Low-friction sliding in graphene and related systems 10FAF05
FOM employees on this project
Name
Position
M.M. van Wijk
PhD
Start date
0 September 2011
End date
31 August 2015
Workgroup FOM-T-17
Leader
Prof.dr. F. Mugele
Organisation
Twente University
Project (title + number)
Nanolubrication on novel low-friction surface 10FAF02
FOM employees on this project
Name
Position
F. Liu
PhD
Start date
16 August 2011
- 10 -
End date
30 September 2015